Embodiments relate to an amplifier. Some embodiments relate to a boost operational amplifier.
A boost operational amplifier may be used to drive a large-scale resistance and/or a capacitive load. Example FIG. 1 is a configurational diagram of a boost operational amplifier, and FIG. 2 is a diagram of a dead zone of a boost operational amplifier illustrated in FIG. 1. Referring to FIG. 1 and FIG. 2, in order to reduce a ripple to instant load switch, a stabilizing capacitor, for example between approximately 1 nF and 100 uF, may be connected to output node N of a boost operational amplifier to use. A boost operational amplifier may have a relatively large size of an output transistor to drive a sufficient output current using a simple configuration. Since a size of an output transistor may be considerably large, a dead zone, for example as shown in FIG. 2, may be provided to at least one side to reduce a standby current.
An output of a boost operational amplifier may form a dead zone, and/or a boost operational amplifier may be normally driven in a course of pull-up and/or pull-down of a boost operational amplifier, but may not be driven during a dead zone interval. Therefore, stability may be substantially maintained in a relatively heavily loaded state and/or current consumption may be minimized. However, since two inputs may be provided to an operational amplifier, offsets mutually generated from two inputs may vary. Therefore, a characteristic of a dead zone may not appear precisely in a controlled region.
Referring to example FIG. 3A, a graph illustrates extension of a dead zone due to an offset difference. Referring to FIG. 3B, a graph illustrated a negative dead zone due to an offset difference. First operational amplifier A1 may have a positive offset and/or second operational amplifier A2 may have a negative offset, such that a DC level and/or a dead zone may relatively increase, for example as illustrated in FIG. 3A. A first operational amplifier A1 may have a negative offset and/or a second operational amplifier A2 may have a positive offset, such that two transistors M1 and/or M2 to output drive may be simultaneously turned on. Therefore, a short current may be generated.
If offsets of first and second operational amplifiers A1 and A2, respectively, are randomly changed, a size and/or position of a dead zone may have variations. Hence, these variations may need to be compensated. If a size of a dead zone becomes considerably small and/or disappears, a large ripple may be generated while a load may be switched. Thus, an externally connected capacitor may be repeatedly charged and/or discharged to increase current consumption. Moreover, if a size of a dead zone relatively increases, a size of a valid offset relatively increases to minimize performance of an operational amplifier.
Accordingly, there is a need of an amplifier, which may include a boost operational amplifier, and methods thereof, which may minimize an offset and/or a variation for a dead zone.